1. Field of the Invention
The present invention relates to a preactivated organophilic clay gellant for lubricating greases and lubricating greases thickened using the gellant. The present invention also relates to a process for preparing a preactivated organophilic clay gellant and to a preactivated organophilic clay gellant made by the process.
2. Background of the Invention
It is well known in the art that organophilic clays can be used to thicken a variety of organic compositions. A problem which is often encountered in using organophilic clay gellants is that to obtain the desired level of thickening, it is necessary to disperse the gellant thoroughly in the composition. Otherwise, a much greater amount of organophilic clay gellant is needed and/or the organophilic clay particles may be larger than other particles (e.g., pigment) present in the composition thereby leading to adverse results (e.g., an unattractive rough coating or settling of the particles) and/or variations in viscosity may occur upon subjecting the composition to shear.
In an effort to achieve proper dispersion of the organophilic clay gellant, the art has explored various avenues. For example, certain organophilic clay gellants, such as shown in U.S. Pat. No. 2,531,440, were mixed with the organic composition to be thickened and the mixture subjected to high shear conditions. Alternatively, low molecular weight polar organic materials known as polar activators, dispersants, dispersion aids, solvating agents, dispersion agents and the like, which may be exemplified by acetone, methanol/water, ethanol/water, propylene carbonate, acetonylacetone, diacetone alcohol, dimethyl formamide and gammabuty-lactone, have been combined with the organophilic clay gellant in order to achieve dispersion into the organic composition. Illustrative patents which disclose these materials are U.S. Pat. Nos. 2,677,661, 2,704,276, 2,833,720, 2,879,229, 2,966,506 and 3,294,683.
One type of organic composition which still typically requires the presence of a polar activator is lubricating grease. Without the presence of a polar activator, which is generally present in an amount ranging up to 50% by weight of the gellant, most organophilic clay gellants do not achieve good dispersibility and/or achieve efficient gelation.
To avoid the danger of storing and using the generally highly volatile and flammable polar activators in the preparation of the thickened organic composition, the art has developed certain alternatives. For example, U.S. Pat. No. 4,435,218 describes a self-activating rheological additive comprising a montmorillonite clay modified with a quaternary ammonium compound and an alcohol which is solid at normal room temperature. The preferred type of solid alcohol has the formula: ##STR1## wherein n is one to five with the preferred alcohol being neopentyl glycol. Other named alcohols are 2-methyl-2-propanol; erythritol; neopentyl alcohol; 2,3,3-trimethyl-2-butanol; monopalmitate glycol; 1,3-dipalmitate glycol; 1-monolaurate glycol; 1-monooleate glycol; 1-monostearate glycol; alpha, beta-dihydroxy stearic acid; and 9,10-dihydroxy octadecanoic [acid].
European Pat. No. 133071 describes the preparation of organophilic clay rheological additives that develop gelling properties in organic liquids at low shear rates without the use of polar activators. The organophilic clays have been modified with a mono- or poly-hydroxylated nitrogeneous surfactant, such as an alkoxylated alkylamine or an alkoxylated quaternary ammonium salt with long hydrocarbon chains.
U.S. Pat. No. 2,767,177 describes the preparation of bentonite-polyamine complexes which consist of the reaction product of bentonite, polyamine and monoquaternary ammonium compounds containing two long chain alkyl groups and are useful for producing gelled greases apparently without a polar activator. The complex of bentonite, the polyamine and the quaternary ammonium compound is used to gel organic materials of a hydrocarbon nature such as liquid petroleum hydrocarbons, mineral oils, lubricating oils, aromatic liquid hydrocarbons, and halogenated hydrocarbons. To prepare the gels, the complex is incorporated into the fluid media by means of high shear mixing equipment such as a colloid mill.
U.S. Pat. No. 3,977,894 describes the preparation of a self-activating organoclay rheological additive for non-aqueous fluid systems. The self-activating organoclay is comprised of a homogenous mixture of an organically modified (with a quaternary ammonium compound) montmorillonite clay and two solid waxes. The waxes are the activators for the organophilic clay and are (1) glyceryl tri-12-hydroxystearate and (2) an amide wax having the formula: ##STR2## where n is from 2 to 18, HSA is the acyl radical of 12-hydroxystearic acid, R is hydrogen or the acyl radical of 12-hydroxystearic acid.
U.S. Pat. No. 4,382,868 describes organophilic clays prepared by extruding a mixture of a smectite clay, a quaternary cationic organic compound, water, and an alcohol having from 1-5 carbon atoms, which are readily dispersible in oleaginous liquids under low shear. By the definition set forth at column 6, lines 34-42, extruding means intimate mixing to cause a reaction between the clay and the organic cationic compound. It is important that the organophilic clay is not dried to remove the water or the alcohol. Representative alcohols are methanol, ethanol, and isopropanol. Additionally, other low molecular weight polar organic liquids can replace the alcohol such as ketones, amides, nitriles, nitrocompounds, esters, and carbonates (e.g., acetone, dimethyl formamide, acetonitrile, nitromethane, methyl formate, and propylene carbonate).
U.S. Pat. No. 4,464,274 is similar to U.S. Pat. No. 4,382,868 and includes organophilic clay gellants prepared from attapulgite or sepiolite clays.